The present invention relates to improvements in a power steering system of the type in which movement of a steering wheel is transmitted via a torsion bar to an oil path switching valve to actuate a power cylinder in a desired steering direction by switching a high pressure oil path extending from an oil pump to the oil path switching valve and a low pressure oil path extending from the oil path switching valve to an oil tank and a part of working oil flowing through the high pressure oil path is led to a reaction piston to restrain torsion of the torsion bar.
Various designs of a power steering system of the above-mentioned type have been heretofore known. However, some known power steering systems of the above-mentioned type had a shortcoming that upon steering under a high speed condition when an output power exceeding a predetermined level is necessitated for a power cylinder there occurs a pressure loss and the feeling of reaction in the proximity of the neutral position of the steering wheel is not sufficient.